Screening And Application Of Lactic Acid Bacteria In Silage Of Typical Steppe Dominant Species

Natural forage is one of the important forage resources,and modulating natural forage into silage can improve the palatability and digestibility of natural forage and solve the problem of insufficient forage supply in winter,but the natural steppe plant communities are complex and diverse,and there are differences in the nutrient composition of each plant,while the research on natural forage silage in China started late,and the research on silage of dominant species is not deep enough,and little research has been reported on the dynamic patterns of silage fermentation quality and microbial community diversity of the dominant species and on specialized lactic acid bacteria additives.Therefore,in this study,the typical steppe dominant species of Leymus chinensis and Stipa grandis were used as the research objects,and the single-and two-factor experimental design was used to clarify the changes of silage quality and fermentation type during the fermentation process using microbiomics and multivariate statistical analysis.The lactic acid bacteria with high acid production capacity and low temperature survival in sheep grass and big needle grass silage were screened.Finally,the screened lactic acid bacteria were used as additives to prepare Leymus chinensis and Stipa grandis silage,and the fermentation effect of screened lactic acid bacteria in the dominant species silage and the effect on the bacterial community composition were clarified.and the fermentation effect of the screened lactic acid bacteria in the silage of dominant species and the effect on the bacterial community composition were clarified.This study aimed to determine the fermentation characteristics of typical steppe dominant species,to explore the resources of lactic acid bacteria additives of dominant species,and to provide a basis for the improvement of natural forage silage quality and the development of lactic acid bacteria additives.The main results have been reviewed as follows:（1）Natural silage affected the nutritional quality of dominant species,significantly（P<0.05）reduced the acidic detergent fiber content of Leymus chinensis and crude fat content of Stipa grandis to 35.44%and 6.41%respectively after 60 days of silage;in terms of fermentation quality,silage significantly（P<0.05）increased the lactic acid content of Leymus chinensis and Stipa grandis to 0.82%and 0.74%respectively after 60 days of silage.In terms of microbial population,silage significantly（P<0.05）increased the number of lactic acid bacteria in Leymus chinensis and Stipa grandis,increasing to 6.63 log cfu·g^-1and 7.46%log cfu·g^-1respectively after 60 days of silage;in terms of bacterial community,the Lactiplantibacillus replaced Pantoea in Leymus chinensis and Kosakonia and Weissella in Stipa grandis as the dominant genera,and decreased to 72.52%and 79.01%respectively after 60 days of silage.（2）A total of 38 strains of lactic acid bacteria were isolated from Leymus chinensis and Stipa grandis raw materials and their silage stages,and two strains with fast acid production rate and low temperature survival were screened by acid production test,temperature tolerance test and physiological and biochemical test,which were identified by16S r RNA gene sequence as Pediococcus pentosaceus PP and Lactobacillus plantarum LP.（3）When PP,LP and LPS were added to Leymus chinensis and Stipa grandis,the lactic acid content increased rapidly and p H decreased rapidly in each group compared with CK.After 60 days of silage,the soluble carbohydrate content of the Leymus chinensis LP group increased by 2.44%compared to the PP group,and the Stipa grandis PP group had a significantly（P<0.05）higher soluble carbohydrate content than the LP group by 11.93%;the lactic acid content was higher in the LP group of Leymus chinensis,and the bacterial community diversity of the LP group was significantly lower than that of CK and PP,and Lactiplantibacillus replaced Pantoea as the dominant bacterial genus in the LP group,with a relative abundance of 94.06%.The lactic acid content was higher in the PP group of Stipa grandis,the diversity of bacterial community in the PP group was significantly lower than the other treatment groups,and Lactiplantibacillus and Pediococcus replaced Pantoea as the dominant bacterial genera with relative abundance of 51.04%and 36.93%respectively,PP was more suitable as lactic acid bacteria additive for Stipa grandis,and LP was more suitable as additive for Leymus chinensis.